I propose to study direct and indirect toxicity of anti-tumor drugs in normal and tumor-bearing mice with respect to dose scheduling, combination drugs and incremental drug doses (chemotherapeutic maneuvers). I suggest that there are two hemopoietic toxicities, i.e., 1) a direct toxicity in depressing bone marrow cellularity and 2) an indirect toxicity which is more selective on the immune response (so called because after continuous chemotherapy cancer patients die of infections without attendant granulocytopenia). The direct and indirect chemotherapeutic indices will be numerically quantified from the experimental data. Normal and leukemic mice will be used for our studies. Methods to be employed are: enumeration of in vivo colony-forming units (CFU), in vitro colony-forming cells (1VCFC), in vitro and in vivo hemolytic plaque forming cells (PFC) and mixed lymphocyte interactions coupled to PFC, in vitro (MLl). Hence, chemotherapeutic maneuvers of anti-tumor agents will be assessed for their effects on hemo-immuno-poiesis.